Device and method for storing or switching

ABSTRACT

A method for storing or switching. The method comprises: arranging a first layer including a first molecular network having a first 2D lattice structure and a second layer including a second molecular network having a second 2D lattice structure at a distance from each other such that the first and the second molecular network interact electronically via molecular orbital interactions, and rotating the first layer relative to the second layer by a rotation angle with a rotation device, wherein an electrical resistance between the first molecular network and the second molecular network changes as a function of the rotation angle, thereby storing information by switching the electrical resistance.

FIELD OF THE INVENTION

The invention relates to a device and a method for storing data or forswitching an electrical resistance. Furthermore, the device and themethod relate to security or encryption applications.

BACKGROUND

The field of electromechanical memory and switching devices, inparticular the field of micro- and nano-electromechanical devices, hasbecome a field of high research activity and technological interest. Thecapability of storing multi-bit information is one of the challenges inmemory technologies. It provides a way to increase the memory densityper volume and may pave the way for an improved design on the systemlevel with higher memory density at lower cost. Efforts have been madeto develop non-volatile memory devices with reliable data storage at lowcost. Among many kinds of memory devices, flash memories which employ afloating gate structure with two programmable charge states are used,wherein their basic operation is based on charge trapping in a floatinggate. Nevertheless, flash technology seems to be limited in scaling ascharge leakage increases and charge separation becomes increasinglydifficult upon scaling down the device dimensions.

US 2013/0321064 A1 discloses a single-molecule switching device. Atunneling current is applied across a tunneling junction, wherein thetunneling junction includes an endohedral fullerene that includes afullerene cage and a trapped cluster. One or more internal motions ofthe trapped cluster are excited because of the tunneling current. Theconductance of the endohedral fullerene is based on the one or moreexcited internal motions. One or more electronic processes arecontrolled based on the changed conductance of the endohedral fullerene.

The current modulation is based on a rotational change of the trappedcluster inside the fullerene cage. In order to induce this rotationalchange a higher bias potential must be applied. The rotational change iscaused by a larger tunneling current through the endohedral fullerene.Therefore, a bias-based switching is disclosed.

BRIEF SUMMARY OF THE INVENTION

According to a first aspect, the invention can be embodied as a device,comprising: a first layer including a first molecular network having afirst 2-dimensional (2D) lattice structure, a second layer including asecond molecular network having a second 2D lattice structure, whereinthe first layer and the second layer are arranged at a distance fromeach other such that the first and the second molecular network interactelectronically via molecular orbital interactions, and a rotation deviceimplemented to rotate the first layer relative to the second layer by arotation angle, wherein an electrical resistance between the firstmolecular network and the second molecular network changes as a functionof the rotation angle.

According to a second aspect, the invention can be embodied as a methodfor storing or switching, comprising: arranging a first layer includinga first molecular network having a first 2D lattice structure and asecond layer including a second molecular network having a second 2Dlattice structure at a distance from each other such that the first andthe second molecular network interact electronically via molecularorbital interactions, and rotating the first layer relative to thesecond layer by a rotation angle with a rotation device, wherein anelectrical resistance between the first molecular network and the secondmolecular network changes as a function of the rotation angle, therebystoring information by switching the electrical resistance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a perspective view of a first embodiment of a device;

FIG. 2A shows molecular building blocks of the first 2D and the second2D layer of the device of FIG. 1 when the molecular networks arealigned, hence interaction by molecular orbitals taking place;

FIG. 2B shows molecular building blocks of the first 2D and the second2D layer of the device of FIG. 1 when the molecular networks aremisaligned, hence no molecular orbital interaction taking place;

FIG. 2C shows a top view of FIG. 2B;

FIG. 2D shows the resistance as a function of the rotation angle for thedevice having a first layer and a second layer as shown in FIG. 2A;

FIG. 3A to 3D show different 2D lattice structures for the first andsecond molecular network as shown in FIG. 2A;

FIG. 4 shows alternative heterogeneous molecular building blocks of thefirst and second 2D layers of FIG. 1 for the case of aligned 2D latticestructures;

FIGS. 5A and 5B show different 2D lattice structures for the first andsecond molecular network as shown in FIG. 4;

FIG. 6 shows the resistance as a function of the rotation angle for adevice having a first layer and a second layer comprising molecularbuilding blocks as shown in FIG. 4;

FIG. 7 shows an arrangement of the first and second layer at preferredrotation angles;

FIG. 8 shows a sequence of the preferred rotation angles shown in FIG. 7with the time;

FIG. 9 shows the current corresponding to the sequence as depicted inFIG. 8;

FIG. 10 shows an alternative position of the rotation axis;

FIG. 11 shows a top view of a second embodiment of a device; and

FIG. 12 shows a cross section of the device of FIG. 11.

Similar or functionally similar elements in the figures have beenallocated the same reference signs if not otherwise indicated.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1 shows a perspective view of a first embodiment of a device 1. Thedevice 1 comprises a first layer 2, a second layer 3 and a rotationdevice 4. The first layer 2 includes a first molecular network 5 havinga first 2D lattice structure. Further, the second layer 3 includes asecond molecular network 6 having a second 2D lattice structure.

First and second layer 2, 3 are arranged at a distance 7 from eachother. The distance 7 is chosen such that the first and second molecularnetwork 5, 6 interact electronically via molecular orbital interactions.The rotation device 4 can rotate the first layer 2 relative to thesecond layer 3 by a rotation angle Θ. That means the first layer 2defines a plane with two orthogonal directions x and y. A rotation axis8 which can be orthogonal to the first and second layer 2, 3 and to thedirections x, y is located somewhere in the first layer 2, preferably inthe center of the first layer 2. The first layer 2 can be rotated by therotation device 4 around the rotation axis 8 by the rotation angle Θ. Inan alternative, the second layer 3 is rotated.

An electrical resistance R is measured between the first molecularnetwork 5 and the second molecular network 6. The electrical resistanceR changes as a function of the rotation angle Θ.

Therefore, the resistance response pattern upon rotational changes ofdevice 1 is functionally independent from an additional bias voltage.This is in particular the case when operating the device as a memory orresistance switching device. The change in resistance is predominantlyinduced by the mechanical rotation.

The first layer 2 including the first molecular network 5 and/or thesecond layer 3 including the second molecular network 6 comprise a firstdimension d₁ and a second dimension d₂. As can be seen in FIG. 1 thefirst dimension d₁ can be smaller than the second dimension d₂. In thiscase the first dimension d₁ can be in the range 1 to 100 nm andpreferably in the range 5 to 50 nm. However, the first layer 2 includingthe first molecular network 5 and/or the second layer 3 including thesecond molecular network 6 can also have a square or circular shape. Inthis case there is only one dimension d, wherein the parameter d can bein the range 1 to 100 nm and preferably in the range 5 to 50 nm.

FIG. 2A shows a first molecular building block 9 of the first layer 2and a second molecular building block 10 of the second layer 3 of thedevice 1 of FIG. 1. As depicted in FIG. 2A the first molecular network 5and the second molecular network 6 are aligned. Therefore, also thefirst molecular building block 9 and the second molecular building block10 are aligned.

The first layer 2 including the first molecular network 5 and/or thesecond layer 3 including the second molecular network 6 can comprisebetween 1 and 500000 molecular building blocks 9, 10, preferably between1 and 1000 molecular building blocks 9, 10 and more preferably between 1and 500 molecular building blocks 9, 10. That means a layer 2, 3 cancomprise a molecular network 5, 6 and the molecular network 5, 6 cancomprise one or more molecular building blocks 9, 10.

For example, the first or second molecular network 5, 6 can beimplemented as graphene-like systems having a cross-sectional extensionin-plane of about 100 nanometers. Then, roughly 100.0000-200.00benzene-like molecular building blocks 9, 10 are involved.

The molecular building block 9, 10 can comprise molecular orbitals 13which can be hybridized orbitals, especially sp² and/or sp^(a) orbitals.That means also the first molecular network 5 and/or the secondmolecular network 6 can comprise hybridized orbitals, especially sp²and/or sp^(a) orbitals.

The first molecular network 5 has a first 2D lattice structure 11 andthe second molecular network 6 has a second 2D lattice structure 12. Ascan be seen in FIG. 2A the first 2D lattice structure 11 and the second2D lattice structure 12 can be identical. The 2D lattice structure 11,12 is given by the number and arrangement of the molecular orbitals 13of the corresponding molecular building block 9, 10 and the distancebetween the molecular orbitals 13 of the corresponding molecularbuilding block 9, 10.

As can be seen in FIG. 2A the molecular orbitals 13 of the firstmolecular network 5 are of the same kind and the molecular orbitals 13of the second molecular network 6 are of the same kind. Also, themolecular orbitals 13 of the first and second molecular networks 5, 6can be of the same kind.

The first layer 2 and the second layer 3 can be arranged such that themolecular orbitals 13 of the first molecular network 5 and the molecularorbitals 13 of the second molecular network 6 provide an electronicinteraction mechanism 14. Furthermore, the electronic interactionmechanism 14 can be implemented to change the electronic overlap as afunction of the rotation angle Θ. When the molecular orbitals 13 of thefirst molecular building block 9 are arranged above the molecularorbitals 13 of the second molecular building block 10 then a molecularorbital 13 of the first molecular building block 9 stronglyelectronically interacts forming a hybridized joint molecular orbital 14to the second molecular building block 10.

FIG. 2B shows the first molecular building block 9 of the first layer 2and the second molecular building block 10 of the second layer 3 of thedevice 1 of FIG. 1. As depicted in FIG. 2B the first molecular network 5and the second molecular network 6 are misaligned.

In contrast to the situation of FIG. 2A in FIG. 2B the first layer 2 hasbeen rotated with rotation angle Θ. As a result the molecular orbitals13 of the first molecular network 5 and the second molecular network 6do not provide an electrical interaction 14 any more. Therefore, in thearrangement of the layers 2, 3 as depicted in FIG. 2B the resistance Rwill be high.

FIG. 2C shows a top view of FIG. 2B. The solid line corresponds to thefirst layer 2, the first molecular network 5 and the first molecularbuilding block 9. The dotted line corresponds to the second layer 3, thesecond molecular network 6 and the second molecular building block 10.

As can be seen when the first molecular building block 9 is arranged tothe second molecular building block 10 as depicted in FIG. 2C there isno molecular orbital interaction leading to current suppression betweenthe molecular orbitals 13 of the different molecular building blocks 9,10.

FIG. 2D shows the electrical resistance R as a function of the rotationangle Θ (solid line) for the device 1 having a first layer 2 and asecond layer 3 as shown in FIG. 2A.

When the molecular orbitals 13 of the different molecular buildingblocks 9, 10 are perfectly aligned above each other (situation as shownin FIG. 2A) then the electrical resistance R has a local minimum. Thatmeans the device 1 is in the on state 15 and a current can flow betweenthe first and second layer 2, 3. When the molecular orbitals 13 of thedifferent molecular building blocks 9, 10 are perfectly misaligned (asituation shown in FIGS. 2B and 2C) then the electrical resistance R hasa local maximum. That means the device 1 is in the off state 16 and nocurrent will flow between the first and second layer 2, 3.

As can be seen in FIG. 2D the on state 15 is only realized at certainrotation angles Θ. In contrast thereto, the device is in the off statefor certain ranges of rotation angles Θ. That is because the electricalinteraction 14 is very sensitive to the rotation angle Θ. For thehexagonal 2D lattice structure 11, 12 as shown in FIG. 2A the on state15 is repeated at an rotation angle Θ of 60°.

FIG. 3A to 3D show different 2D lattice structures 11, 12 for a firstand second molecular network 5, 6 as shown in FIG. 2A. As describedbefore, the 2D lattice structure 11, 12 is given by the number of themolecular orbitals 13, by the arrangement of the molecular orbitals 13and by the distance between the molecular orbitals 13.

In FIG. 3A to 3D is always only one molecular building block 9, 10depicted. The first 2D lattice structure 11 and/or the second 2D latticestructure 12 can have an arbitrary shape. Especially, the first 2Dlattice structure 11 and/or the second 2D lattice structure 12 can havea hexagonal shape (see FIG. 3A), a pentagonal shape (see FIG. 3B), asquare shape (see FIG. 3C) and a triangular shape (see FIG. 3D).

FIG. 4 shows alternative molecular building blocks 9, 10 of the firstand second layer 2, 3 of FIG. 1 when the molecular networks 5, 6 arealigned. As can be seen from FIG. 4 there are two kinds of interactingmolecular orbital situations. There are first molecular orbitals 13 aand second molecular orbitals 13 b. Further, there are first electricalinteractions by hybridized orbitals 14 a between first molecularorbitals 13 a of two different molecular building blocks 9, 10 and thereare second electrical interactions by hybridized orbitals 14 b betweensecond molecular orbitals 13 b of two different molecular buildingblocks 9, 10.

In principal, the first molecular network 5 and the second molecularnetwork 6 can comprise molecular orbital interactions of several kinds13 a, 13 b, especially two, three or four kinds of molecular orbitalinteractions 13.

FIGS. 5A and 5B show different 2D lattice structures 11, 12 for a firstand second molecular network 5, 6 as shown in FIG. 4. As can be seen inthese 2D lattice structures 11, 12 first molecular orbitals 13 aalternate with second molecular orbitals 13 b. FIG. 5A shows a hexagonal2D lattice structure 11, 12 and FIG. 5B shows a square 2D latticestructure 11, 12.

FIG. 6 shows the electrical resistance R as a function of the rotationangle Θ for a device 1 having a first layer 2 and a second layer 3 asshown in FIG. 4. The electrical resistance R reaches a local maximum,i.e. an off state 16, when the first molecular network 5 and the secondmolecular network 6 are perfectly misaligned. However, there are twolocal minima 15 a, 15 b of the electrical resistance R. The first localminima, i.e. the first on state 15 a, is reached when the molecularorbitals 13 a and the molecular orbitals 13 b of the two differentlayers 2, 3 are aligned. The second local minima, i.e. the second onstate 15 a, is reached when the molecular orbitals 13 a of one layer 2,3 are aligned with molecular orbitals 13 b of the other layer 3, 2.

The first molecular network 5 and/or the second molecular network 6 isone of the group of: benzene, graphene, phenyl, oligophenyl, pyridine ortetrathiafulvalene. A preferred material can be phenyl with distinct sp²orbitals. More complicated are oligophenyles which possess conjugatedπ-systems and the pitch between them is defined by C—C single, double ortriple bonds (C: carbon). Substitution of the C can lead in artificialstructures, namely pyridines, tetrathiafulvalene (TTF), etc. Themolecular building blocks 9, 10 can be self-linking to each other due tothe attractive forces in the orbital landscape, e.g. the p-p stacking inphenyl.

FIG. 7 shows an arrangement of the first and second layer 2, 3 atpreferred rotation angles Θ. The example of FIG. 7 shows a first and asecond layer 2, 3 comprising graphene. FIG. 7 shows four differentfigures for four different rotation angles Θ. In a first figure thefirst layer 2 is rotated by a rotation angle Θ of 0°. That means thefirst layer 2 is not rotated with respect to the second layer 3. In asecond figure the first layer 2 is rotated by a rotation angle Θ of 10°.In a third figure the first layer 2 is rotated by a rotation angle Θ of21.8°. And in a fourth figure the first layer 2 is rotated by a rotationangle Θ of 38.2°.

There are locations 17 where a first molecular building block 9 and asecond molecular building block 10 are aligned. The more of theselocations 17 are present at a rotation angle Θ the lower the electricalresistance R between the first and the second layer 2, 3 is. As can beseen in FIG. 7 the most of these locations 17 can be found by a rotationangle Θ of 0° and no of these locations 17 can be found for a rotationangle Θ of 10°. For a rotation angle Θ of 21.8° more of these locations17 can be found than for a rotation angle Θ of 38.2°.

The first layer 2 and the second layer 3 can be arranged such that theelectrical resistance R has a local minimum at preferred rotationangles. For a first layer 2 and a second layer 3 comprising graphene,such preferred rotation angles Θ are 0°, 21.8° and 38.2°.

FIG. 8 shows a sequence of the preferred rotation angles Θ shown in FIG.7 with the time t.

FIG. 9 shows the current A corresponding to the sequence as depicted inFIG. 8. As can be seen the highest current A will flow between firstlayer 2 and second layer 3 for an rotation angle Θ of 0°. There willflow some current A for a rotation angle Θ of 21.8° and there will flowno current A for a rotation angle Θ of 10°.

FIG. 10 shows an alternative position of the rotation axis 8. Therotation device 4 is implemented to rotate the first layer 2 relative tothe second layer 3 about the rotation axis 8, wherein the rotation axis8 is located outside the first and second layer 2, 3.

FIG. 11 shows a top view of a second embodiment of the device 1. Therotation device 4 comprises at least one actuator 18 coupled to thefirst or second layer 2, 3. Especially, the rotation device 4 cancomprise one, two, three, four or five actuators 18. The device 1 shownin FIG. 11 comprises two actuators 18.

The device 1 can comprise a housing 19. Further, the rotation device 4can comprise guide arms 20, wherein the actuators 18 are arranged in theguide arms 20. The guide arms are connected with the first or secondlayer 2, 3 and the housing 19. Therefore, the guide arms 20 can guidethe rotation of the first layer 2 with respect to the second layer 3 orvice versa.

In an alternative the guidance and the actuation can be separated. Theguidance can be realized by a bearing. Further, the actuation can berealized with an electro motor, by using a magnetic effect or by using apiezo effect.

Each of the first and the second layer 2, 3 can be in electrical contactwith a metal layer 21. Each of the metal layers 21 are contacted byelectrical contacts 22.

FIG. 12 shows a cross section of the device of FIG. 11 along the XI-XIline. As can be seen the device 1 can further comprise a device 23 forinjecting a current across the first and second layer 2, 3. The device 1can also comprise a device 24 for measuring the current flowing from thefirst to the second layer 2, 3. Especially, the device 24 for measuringthe current measures the current injected by the device 23 for injectinga current. The device 24 for measuring the current and the device 23 forinjecting a current can be one single device.

The device 24 for measuring the current further comprises a first and asecond metal layer 21 a, 21 b, wherein the first layer 2 is in contactwith the first metal layer 21 a and the second layer 3 is in contactwith the second metal layer 21 b. Further, a first electrical contact 22a can establish an electrical connection between the first metal layer21 a and the device 24 for measuring the current. Also, a secondelectrical contact 22 b can establish an electrical connection betweenthe second metal layer 21 b and the device 24 for measuring the current.

As shown in FIG. 12 the second layer 3 and the second metal layer 21 bcan be arranged on a carrier 25. The first layer 2 and the first metallayer 21 a can rotate with respect to the second layer 3 and the secondmetal layer 21 b.

The first layer 2 can include several first molecular networks 5 layeredin a stack and/or the second layer 3 can include several secondmolecular networks 6 layered in a stack. Handling of the device 1becomes easier when each of the first and second layer 2, 3 comprisesseveral molecular networks 5, 6 layered in a stack.

Further a method for storing data or for switching an electricalresistance R is described. The method comprises arranging a first layer2 including a first molecular network 5 having a first 2D latticestructure 11 and a second layer 3 including a second molecular network 6having a second 2D lattice structure 12 at a distance 7 from each othersuch that the first and the second molecular network 5, 6 interactelectrically. The method further comprises rotating the first layer 2relative to the second layer 3 by a rotation angle Θ with a rotationdevice 4. Thereby, an electrical resistance R between the firstmolecular network 5 and the second molecular network 6 changes as afunction of the rotation angle Θ.

Therefore, by manipulating the rotation angle Θ an electrical resistanceR can be stored. Further, by manipulating the rotation angle Θ anelectrical resistance R can be switched. For security, a series ofcurrent signals can be associated with a series of rotation angles Θ.The device and method therefore allow for a non-volatile resistance orinformation storage. In particular, the resulting relative electricalresistance with respect to different rotational angles is generallydefined by the respective angle and not by an additional bias voltageacross the layer system. Multilevel memory elements are also feasible.

The electrical resistance R can be stored or switched by a rotationangle Θ in the range of 0.001° and 0.1°, preferably in the range of0.005° and 0.015°. A sensitivity of 0.01° for rotational changes can berealized.

More generally, while the present invention has been described withreference to certain embodiments, it will be understood by those skilledin the art that various changes may be made and equivalents may besubstituted without departing from the scope of the present invention.In addition, many modifications may be made to adapt a particularsituation to the teachings of the present invention without departingfrom its scope. Therefore, it is intended that the present invention notbe limited to the particular embodiments disclosed, but that the presentinvention will include all embodiments falling within the scope of theappended claims.

REFERENCE SIGNS

-   1 device-   2 first layer-   3 second layer-   4 rotation device-   5 first molecular network-   6 second molecular network-   7 distance-   8 rotation axis-   9 first molecular building block-   10 second molecular building block-   11 first 2D lattice structure-   12 second 2D lattice structure-   13 molecular orbital-   13 a first molecular orbital-   13 b second molecular orbital-   14 electrical interaction-   14 a first electrical interaction-   14 b second electrical interaction-   15 on state-   15 a first on state-   15 b second on state-   16 off state-   17 location-   18 actuator-   19 housing-   20 guide arm-   21 metal layer-   21 a first metal layer-   21 b second metal layer-   22 electrical contact-   22 a first electrical contact-   22 b second electrical contact-   23 device for injecting a current-   24 device for measuring the current-   25 carrier-   x direction-   y direction-   Θ rotation angle-   R electrical resistance-   d dimension-   d₁ first dimension-   d₂ second dimension-   t time-   A current

The invention claimed is:
 1. A method for storing or switching,comprising: arranging a first layer including a first molecular networkhaving a first 2D lattice structure and a second layer including asecond molecular network having a second 2D lattice structure at adistance from each other such that the first and the second molecularnetwork interact electronically via molecular orbital interactions, androtating the first layer relative to the second layer by a rotationangle with a rotation device, wherein an electrical resistance betweenthe first molecular network and the second molecular network changes asa function of the rotation angle, thereby storing information byswitching the electrical resistance.
 2. The method according to claim 1,wherein the electrical resistance is stored or switched by a rotationangle in the range of 0.001° and 0.1°.
 3. The method according to claim2, wherein the electrical resistance is stored or switched by a rotationangle in the range of 0.005° and 0.015°.
 4. The method according toclaim 1, wherein a resistance response pattern upon rotational changesis functionally independent from an additional bias voltage appliedacross the first and/or second layers.
 5. The method according to claim1, wherein the first molecular network and/or the second molecularnetwork comprise molecular orbitals.
 6. The method according to claim 5,wherein the molecular orbitals are sp² and/or sp^(a) molecular orbitals.7. The method according to claim 5, further comprising: arranging thefirst layer and the second layer such that the molecular orbitals of thefirst molecular network and the molecular orbitals of the secondmolecular network electrically interact interaction based on molecularorbital interactions, and changing an electronic overlap as a functionof the rotation angle.
 8. The method according to claim 5, wherein thefirst molecular network and the second molecular network comprisemolecular orbitals of the same kind.
 9. The method according to claim 5,wherein the first molecular network and the second molecular networkcomprise two, three or four kinds of molecular orbitals.
 10. The methodaccording to claim 1, wherein the first molecular network and/or thesecond molecular network is one of the group of: benzene, graphene,phenyl, oligophenyl, pyridine or tetrathiafulvalene.
 11. The methodaccording to claim 1, further comprising using the rotation device torotate the first layer relative to the second layer about a rotationaxis, wherein the rotation axis is located inside or outside the firstand second layer.
 12. The method according to claim 1, wherein the firstlayer and the second layer are arranged such that the electricalresistance has a local minimum at preferred rotation angles.
 13. Themethod according to claim 1, further comprising: injecting a currentacross the first and second layer.
 14. The method according to claim 1,further comprising: measuring the current flowing from the first to thesecond layer.